humic coal of a high degree of metamor-phism. With a microscope plant residues can be discerned.
Anthracite is black, often with a grayish shade, with an occasional spotty iridescence. It gives a velvety black line on a porcelain plate. Its luster is high and metallic. It is highly viscous, does not sinter, and conducts electricity well. It has a strong, metallic luster. Its highest hardness on the mineralogical scale is 2.0–2.5; its density of organic mass is 1,500–1,700 kg/m3. Heat of combustion of organic mass is 33.9–34.8 megajoules per kg (8,100–8,350 kcal/kg). Anthracite has a low analytical moisture content of 1–3 percent, and its combustible mass contains up to 9 percent volatiles, 93.5–97.0 percent carbon, 1–3 percent hydrogen, and 1.5–2.0 percent oxygen and nitrogen. Anthracite containing more than 97 percent carbon in the combustible mass is called superanthracite. According to the volume yield of volatiles, it is divided into two commercial grades: semianthracite, containing 220–330 liters per kg, and anthracite as such, with a volume yield below 220 liters per kg.
Anthracite occurs in the form of beds of different thicknesses, usually intermediate and thin—rarely up to 10–40 m thick—in deposits of many geological systems from the Devonian to the Triassic. The total anthracite deposits are comparatively small and amount to approximately 3 percent of the world’s coal reserve. The largest quantity of anthracite is located in the USSR (the Donets and Kuznets basins, for example). Considerable anthracite deposits exist in China and the USA. Anthracite is used as a high-quality energy-producing fuel (according to its uses, a distinction is made in industry between gas-generating anthracite and anthracite for the production of calcium and carbide) and also in the manufacture of electrodes and semiconductors. Special grades of anthracite which do not crack during combustion are used in casting and blast furnace processes.
A. K. MATVEEV